#include<iostream>
#include<cstring>
using namespace std;
const int N = 1e5 + 10;
int n, k;
int main()
{
	int sum = 0;
	cin >> n >> k;
	for (int i = 0; i < n; i++) {
		int x;
		cin >> x;
		sum += x;
	}
	cout << sum / n << ".";
	int x = sum % n;
	while (k--) {
		x *= 10;
		cout << x / n;
		x %= n;
	}
	return 0;
}

